Multicompartment Photonic Microcylinders toward Structural Color Inks

Structural coloration is promising as an alternative to chemical coloration because it has characteristics of their high color brightness, no fading, and low toxicity. Here, we report a pragmatic micromolding technique to create functional photonic microcylinders which are useful as structural color pigments. Photocurable dispersions of silica particles with interparticle repulsion are molded to spontaneously form regular arrays in confined volumes, which are instantly stabilized by photopolymerization. The resulting photonic microcylinders, released from the mold, exhibit pronounced structural colors from the entire visible range. In addition, multiple compartments can be integrated into single microcylinders through volatile-solvent-mediated sequential molding. As each compartment can be independently rendered to be structurally colored, transparent, or magneto-responsive, the multicompartment microcylinders show advanced functionalities, such as color-brightness tunability and switchable color properties. These photonic microcylinders will serve as structural color pigments in a wide range of aesthetic coatings and authentication tags.